The present invention relates generally to collecting laser ablated particles, and more particularly to the filtering of the ablated particles resulting from imaging on a medium with a high energy laser.
In the prepress printing industry, it is well known that a substrate such as a film or printing plate (hereinafter collectively referred to as a xe2x80x9cmediumxe2x80x9d) can have an image transferred thereto by selectively xe2x80x9cburningxe2x80x9d areas of a thermally-sensitive surface of the medium with a high energy laser. This method of imaging is generally referred to as thermal imaging. Typically, the power necessary for such image transfer is attained through the use of a laser light source for emitting the high energy laser beam. The specific chemical makeup of the medium will dictate the required characteristics of the light source which are necessary to adequately burn an image onto the medium. Alternatively, the medium can be manufactured so as to have the appropriate chemical makeup to allow imaging with a light source having predetermined characteristics.
In an internal drum imagesetter or platesetter (hereinafter collectively referred to as an xe2x80x9cimagerxe2x80x9d) a medium is typically positioned on the internal cylindrical surface of the drum prior to imaging. When a laser beam is emitted onto the thermally-sensitive surface of the medium positioned within the imager to form the desired image, laser ablation occurs. Laser ablation refers to the loss or removal of material such as melting or vaporization, due to the application of a high energy laser beam with sufficient energy to expose the medium. The material can effectively explode from the surface of the medium, resulting in ablated particles. Thermal imaging thus generates a gaseous, odorous plume of smoke and dust, which include particulate matter.
Existing filtration systems are designed to collect and filter the ablative particles generated during imaging. However, existing filtration systems have several problems. For example, the filtration system may operate improperly for various reasons, such as improper installation of a filtering element, saturation of a filtering element with ablative particles, or the non-operation of the air mover subsystem to specification. Typically the only way to determine when a conventional filtration system is operating improperly is either to periodically inspect the filtering elements and the air mover or to make such inspections when the quality of the imaged media degrades to an unacceptable level due to the accumulation of ablative particles in the imager. Additionally, in conventional filtration systems ablative particles are prone to enter the surrounding environment when a filter, saturated with ablative particles, is removed from the system for replacement. Such emissions can be undesirable whether or not the escaping particles exceed the permissible exposure levels (PEC) at which the particles can become hazardous to humans. Ablative particles may not be properly filtered by conventional filtration systems during operation of the imager if a filter access door or other opening in the filtration system housing is not properly closed or sealed prior to initiating imaging operations. Additionally, conventional ablative particle filtration systems tend to transmit excessive noise to the surrounding environment during operation.
Therefore a need exists for an improved filtration system for ablative particles.
Accordingly, it is an object of the present invention to provide an improved ablative particle filtration technique.
Additional objects, advantages, and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detailed description, as well as by practice of the invention. While the invention is described below with reference to preferred embodiment(s), it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of significant utility.
In accordance with the invention, a filtration system includes a filtration unit operable to filter ablative particles generated by thermal imaging of media. The ablative particles may, for example, be generated by an imaging unit. The filtration unit, or in accordance with certain implementations the imaging unit, is configured to transmit a signal corresponding to a parameter representing a current state of the operation of the filtration unit. Advantageously, the filtration unit and/or imaging unit include one or more sensors for generating the transmitted signal.
The parameter could be any appropriate parameter indicative of the unit operation. For example, the parameter could be a pressure related parameter, which might be sensed by a pressure sensor, and is preferably a change in pressure exceeding a predetermined threshold value. The parameter could alternatively be a power parameter, such as voltage or current, such as that flowing through an electro-mechanical sensor, e.g. a switch, when it closes a circuit. A still further alternative could be a light parameter, such as that which might be sensed by an optical sensor. Of course, if desired, signals representing multiple different parameters could be transmitted.
The represented current state of operation preferably includes a current state of one or more filters. For example, the parameter could indicate that a filter is fully saturated, improperly installed and/or not installed. The represented current state of operation could additionally or alternatively be the current state of an air-mover, perhaps indicating that the air mover is improperly operating and not operating at all. Furthermore, the represented current state of operation could also or alternatively be the current state of a filter access door, and could for example be indicative of a filter access door not being properly closed, which may or may not be related to whether or not the door is properly latched. The represented current state of operation might also or alternatively be the current state of a filter clamp, and could for example be indicative of a filter clamp being properly positioned, which may or may not relate to whether or not the clamp is properly locked in position. The represented current state of operation could additionally or alternatively be a positioning of the filtration unit, by for example the operator, relative to the imaging unit.
A processor receives the transmitted signals and generates, responsive to the receipt of the transmitted signal, a signal representing operator information associated with the current state of operation. The represented operator information could, for example, be a warning and/or a process. The warning could simply be a statement such as xe2x80x9cfiltration unit not properly operating- do not attempt imagingxe2x80x9d, or xe2x80x9csaturated filterxe2x80x9d, or xe2x80x9cfilter door openxe2x80x9d, or xe2x80x9cfilter not installedxe2x80x9d. The process could be instructions for correcting the deficiency in the current state of operation. For example, the signal might represent instructions for changing the appropriate filter, or checking the installation of the appropriate filter, or checking the appropriate filter access door, or checking if the unit is plugged into the power source.
In one embodiment of the invention, the filtration unit, may include a plurality of filters, disposed within a housing, for filtering ablative particles generated by thermal imaging of media. A plurality of sensors, each configured to detect the applicable parameter representing the current state of a respective one of the plurality of filters may also be disposed within the housing.
Advantageously, the embodiment includes a plurality of indicator lights, although this is not mandatory. Beneficially the lights are attached to an outer surface of the housing. If included, each of the lights is configured to illuminate if the parameter detected by a respective one of the plurality of sensors corresponds to a predefined threshold value. The illumination of each of the plurality of indicator lights could, for example, represent saturation of an associated filter.
An air-mover disposed within the housing for moving the ablative particles to each of the plurality of filters may also be included. In such a case, the parameter detected by one of the plurality of sensors could also represent a current state of the air-mover. optionally, an indicator light can be illuminated if the current state of the air-mover operation does not conform to a predetermined standard, e.g. does not create a pressure within a particular threshold.
Typically, although again this is not mandatory, one or more access doors, which are movable to provide access to one or more of the filters, will be included in the unit. In such case, the parameter detected by one or more of the sensors preferably represents a current state of the access door. These sensors may be of a different type from those used to detect the state of the filters and air mover. For example, simple electro-mechanical switches or optical sensors may be highly suitable for use in determining the state of an access door. Here again, if indicator lights are provided, one or more of the lights could, if desired, be configured to illuminate if the current state of an associated access door is not properly closed.
If clamps or other mechanisms are used in the installation of the filters, the parameter detected by one or more of the sensors may optionally represent a current state of the clamp, and thereby indicate whether or not the filter is properly installed. These sensors may also be of a different type from those used to detect the saturation state of the filters or the operational state of the air mover. Again, simple electro-mechanical switches or optical sensors may be highly suitable for use in determining the state of a clamping or other mechanism. Once again, if indicator lights are provided, one or more of the lights could, if desired, be configured to illuminate if a clamp or other mechanism is not properly positioned, e.g. locked in place.
In a particularly advantageous implementation, the filters include a coarse ablative particle filter, a fine ablative particle filter and an adsorbent cell disposed in series along the flow path of the ablative particles. The sensors include a first sensor disposed downstream of the coarse ablative particle filter, a second sensor disposed downstream of the fine ablative particle filter, and a third sensor disposed upstream of the air-mover and downstream of the fine ablative particle filter. Using this sensor configuration, the first sensor could be used to detect a saturated coarse ablative particle filter, the second sensor could be used to detect a saturated fine ablative particle filter, and the third sensor could be used to detect an improperly or non-operating air-mover.